Electric heater



Jan. 15, 1946. H. L NEWELL ELECTRIC HEATER Filedllay29, 1944 7 InventoryHebe? L. Newell,

His Attorney.

Patented Jan. l5, 1946 s PATENT oFTFIcI-J ELECTRIC manna Heber L.Nowell, Bridgeport, Coma, assignor to General Electric Company, acorporation of New York Application May 29, 1944, Serial No. 537,801

Claims.

This invention relates to electrically heated devices, more particularlyto such electrically heated devices as electric blankets, electricheating pads and the like which have one or more heating elements, eachelement comprising a relatively long length of heating wire and one ormore thermostats connected therein, and it has for its object animproved heater of this character.

In heating devices of this character, it has been common practiceheretofore to make up each heating element-prior to its assembly withthe heating device-by connecting the thermostats in proper circuitrelation with a heating wire, and

at such points as will cause the thermostats to be located at thecorrect positions in the device after the heating element is assembledtherein.

It'is diflicult to handle such heating elements, particularly where theyhave a relatively long length such as are required in electric blankets.This is especially true where the blanket has channels formed thereinfor receiving the heating element, because here the heating wire withthe thermostats connected in it must be threaded back and forth throughthe channels into a number of convolutions. And here also. the threadingoperation is likely to impose detrimental stresses in the connectionsbetween the wire and the thermostats.

Moreover, in electrically heated devices where the heating element inany case is enclosed withbeen once assembled, since the body must bethat when the thermostat circuit is inserted, the thermostat is properlylocated in the heating de vice. Moreover, after being inserted in thedevice. the thermostat circuit can be readily connected with the heatingwire so that the thermo stat is properly connected with the heatingwire.

In one specific application of this invention to an electrically heatedblanket, the blanket is provided with a cavity in the'heated bodythereof in which at least a portion of the thermostat circuit isinsertable. This portion includes the thermostat so that when it isinserted the thermostat is brought into proper relation to the body.Moreover, the heating wire and the thermostat circuit are provided withsets of terminals which are brought into close relation when thethermostat circuit is inserted in its cavity so that they can readily bejoined together after the thermostat circuit has been inserted. Theterminals are arranged so that when they are interconnected thethermostat will be properly connected with the heating wirefor examplein series with it.

For a more complete understanding of this invention, reference should behad to the accompanying drawingin which Fig. 1 is a lan view taken apartto gain access to the element, or in causes of failures of such heatingdevices are due to improper connections between the thermostats and theheating wire and to failures of the thermostats themselves it isdesirable that such heating devices be constructed and arranged so as toreduce to a minimum the number of wire connections thathave to be madein assembling the heating element; and moreover, that it be possi blereadily to remove the thermostats from the device independently of theheating wire.

It is an object of this invention to obtain these desired results. i

In accordance with this invention, the heating wire is a separatecontinuous wire, and the thermostat is connected into a separate controlcircult which may be readily inserted in and removed from the heatingdevice independently of the of an electrically heated blanket embodyingthis invention, a part being broken away so as to illustrate certaindetails of construction; and Fig. 2 is a perspective expanded view ofthe blanket of Fig. 1 illustrating a certain element removed from theblanket and the relationship it has with other elements or the blanket.V 7 Referring to the drawing, this invention has been shown in one formas applied to an electrically heated blanket comprising a flexible.blanket body i0. The blanket body I0 is provided with a central area IIwhich is heated, and with a marginal unheated area I! completelysurrounding the heated area I I, as shown.

The heated section II is provided with a series of substantiallyparallel channels l3 which receive a heat generating wire ll. This wirewhen threaded through the channels I3 is formed into a series ofconvolutions extending substantially throughout theentire area of thecentral heated section II. As shown the end turns of the convolutionslie within the margins at the two sides heating wire. The thermostat isso connected spaced intervals indicated by the dotted lines ll in orderto form the channels II, the outside edges of the sheetsbeing leftseparate so as to form the marginal section I. If desired, the top andbottom sheets may be sewed together along the line H; or the channelsmay be formed at the time the blanketis woven, as described in theUnited States patent to Moberg No. 2,203,918, dated June 11, 1940.

As shown, the heating wire i4 is divided into two heating sections 14aand Nb which substantially cover the respective halves of the heatedsection ii, as clearly shown in the drawing. The inner ends of these twoheating sections Ila and b end in terminals l8 and I9 respectively,while the oute ends of the two heater sections are Joined together by acommon terminal 20. The terminals i8, i and 20 are located outside ofthe channels, and about at the center of the blanket adjacent one edgethereof, as shown.

The heating element i4 is provided with a separate thermostat circuit 2i, as shown more clearly in Fig. 2. This circuit comprises a conductingwire formed into two substantially L-shaped loops having correspondingarms 22 and 22a, and corresponding arms 23 and 23a. The inner wires 24and 25 of the two arms 22 and 220 have con nected therein pairs ofthermostats 26 and 21, and 28 and 29, respectively. It will beunderstood that these thermostats may have any suitable construction,and will be provided with suitable terminals (not shown) for connectionwith the conducting wires of the loops. The outer corresponding wires 30and 3| of the two arms 22 and 22a respectively are in substantiallyparallel relation with the two wires 24 and 25, and they terminate intransverse wire sections 32 and 33 which form the outer wires of theother two arms 23 and 23a of the thermostat circuit. These two sections32 and 33 are electrically and mechanically interconnected by means of atermmal 34. The inner wires 35 and 36 of the two arms 23 and 23arespectively-parallel to wires 32 and 33- terminate in end terminals 31and 38.

Connected with the terminal 34 is one con-l ductor 39 of a twin supplyconductor 40. The other conductor 4| of this twin supply conductorterminates in a terminal 42.

The blanket body i0 is further provided with a pair of special channels43 and 44 positioned adjacent the two ends of the blanket and insubstantially parallel relation with the channels II that receive theheating wire. These two channels 43 and 44 are adapted to receive thetwo opposed arms 22 and 22a of the thermostat circuit, and when thesetwo arms are inserted within these channels, the other two arms 23 and23a of the thermostat circuit lie between the upper and lowerunconnected sheets and [6 in the margin of the blanket on the side ofthe blanket which has the heater wire terminals l8, l9 and 20, all ofwhich also are located in the margin between the two unattached blanketsheets. Thus, the thermostat circuit is laterally insertable into theblanket, and when so inserted the thermostat circuit terminals 34, 31,38 and 42 are brought contiguous to the contacts-l8, l8 and of theheater wire.

After the thermostat circuit has been assembled with the blanket, theterminal l8 will be con nected with the terminal 31, the terminal I!will be connected with the terminal 38 and the terminal 20 will beconnected with the terminal 42 of the supply cord. These connections maybe made in any suitable way, as by soldering or brazing, or by means ofscrew terminal members (not shown). This connects the two thermostats 2iand 21 in series with the half heater section 14a, and the twothermostats 28 and 29 in series with the half heater section i4b.

After the thermostat circuit has been assembled, the two separatemarginal sheets may be sewn together at the edges or may be sewn andprovided with a suitable binding.

If it be desired to repair one of the thermostats or to repair aconnection between any of the thermostats and their conducting wires itis merely necessary to open the blanket at its marginal oute edge so asto expose the two sets of tenninals ll, I9 and 20, and 34, 31, 38 and42; these may then be disconnected and the thermostat circult removed inorder to make the necessary repairs. Obviously, all of this can be donewithout disturbing the heating wires. In some cases, the section of themarginal seam opposite th terminals is left open, say for a length ofsix or eight inches, so that the connections and disconnections can bemade conveniently.

Another advantage of this blanket construction is that it is onlynecessary to handle the heating wire itself in threading it into theblanket channels, rather than to handle the heating wire withthermostats already connected in it, as in the practice heretofore used.

The thermostatic circuit in the specific embodiment of the inventionillustrated in the drawing is a protective circuit in that thethermostats are placed to prevent temperature rise in various portionsof the blanket above a predetermined safe value.

It will be understood that while the heating wire l4 has been shown asformed into convolutions extending crosswise of the blanket, they may beand in many cases preferably should be laid lengthwise of the blanket.In such case, the heater sections Na and ill) will be located onopposite sides of the longitudinal cente line of the blanket; and hereit is preferable that the control circuit channels 43 and 44 are locatedthird or fourth from the sides so that there is no danger of their beingtucked in at the sides. It will also be understood that here it ispreferable to locate the terminals ll, I! and 20 at the middle of thebottom of the blanket.

While I have shown a particular embodiment of my invention, it will beunderstood, of course, that I do not wish to be limited thereto sincemany modifications may b made, and I, therefore, contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electrically heated blanket and the like comprising a body formedwith a channeled heating section having therein a first channel for aheating wire and a separate second channel for a protective circuit, andsaid body also having a marginal area at the ends of said channels, acontinuous heating wire located in said first channel and havingelectric supply terminal means connected therewith andlocated outside insaid marginal area. and a protective circuit for said blanket separatefrom said conducting wire comprising a temperature responsive elementand an electrical conducting wire connected with it and said conductingwire being insertable into said second channel from said marginal areaand when inserted therein positioning said temperature responsiveelement in said channel and in proper thermal relation with saidchanneled heating section, and said electrical conducting wire alsohaving a portion outside of said channeled section and located in saidmarginal area,

terminal means connected to said portion for connection with saidfirst-named terminal means, and means for electrically interconnectingsaid terminal means so that said temperature responsive element isconnected in predetermined circuit relation with said heating wire.

2. An electrically heated blanket and the like having a flexible bodyformed with a-series of substantially parallel channels therein, aheating wire threaded in said channels so as to be distributed in aseries of convolutions through a major portion of the area of said body,and

having a set of terminals located outside of said and said circuitfurther having terminals located outside of said channels and adjacentsaid firstnamed set of terminals when said thermostat is inserted sothat said sets of terminals may be readily joined, and the thermostatcircuit being such that when said terminals are joined said thermostatis connected in series relation with said heating wire.

3. .An electrically heated blanket and the like having a flexible bodyformed with a series of substantially parallel channels therein, aheating wire threaded in said channel so as to be distributed in aseries of convolutions through a major portion of the area of said body,and

having a set of terminals located outside of said channels adjacent thecenter of said body at an edge thereof, said body havinga thermostatchannel adjacent one end thereof, a control circuit for said wireincluding a thermostat and a conducting wire formed into an L-shapedloop, one arm thereof including said thermostat being inserted into saidthermostat channel and the other arm of said loop extending from saidchannel along said edge of said body substantially to the center thereofwhere said terminals are located, and said control circuit furtherhaving a set of terminals located adjacent said first-named set whensaid control circuit is assembled with said body whereby they may bereadily connected to them.

4. An electric blanket and the like comprising a blanket provided with aseries of substantially parallel channels therein and having a marginalportion formed by separate opposed sheets and located at the ends ofsaid channels at one edge of the blanket body, a heating wire threadedthrough said channels, said wire being provided with a set of terminalslocated within said marginal portion between said sheets, said body alsohaving a separate thermostat channel having one end opening into saidmarginal Portion, a thermostat circuit for said wire in-' cluding aconducting wire-formed into a loop insertable into said thermostatchannel and having connected therein a thermostat, said thermostatcircuit also including a conducting wire section located within saidmarginal portion between said sheets and having a set of terminalsbrought into contiguous relation with said firstnamed set when saidcontrol circuit is assembled with said body, and which when connectedwith said first named set connects said thermostat in v temperatureresponsive element and a length of conducting wire having saidtemperature responsive element connected therein and said wire beingformed into a loop insertable into said protective circuit channel andwhen inserted therein positioning said temperature responsive element inproper thermal relation with said channeledheating section, and saidwire further having a pair of terminals which are positioned in saidmarginal area adjacent said first-named terminals when said loop isinserted in said protective circuit channel, and said assembly alsohaving a twin supply conductor, and means electrically connecting oneconductor thereof with one side of said loop, and means electricallyconnecting the other side of said loop with one ter minal of saidheating wire and the other conductor of said supply conductor with theother terminal oi. said heating wire, whereby said temperatureresponsive element is connected in se ries circuit relation with saidheating wire.

HEBER L. NEWELL.

